2018/02/21 by Liuti, Simonetta, Engelhardt, Michael, Rajan, Abha
#FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph)
paper · doi:10.48550/arxiv.1802.07688
New Lorentz Invariance Relations (LIRs) were presented between twist-three Generalized Parton Distributions (GPDs) and transverse momentum, kT, moments of twist-two Generalized Transverse Momentum-Dependent Distributions (GTMDs). By implementing both these LIRs and the QCD Equations of Motion in the quark quark correlation function, we generated a new series of Wandzura Wilczek (WW) relations in the off-forward sector. Two of these WW relations take on a particularly interesting physical meaning in that they provide a clear interpretation of the QCD structure of Orbital Angular Momentum (OAM) in the nucleon. In particular, they provide a solution to the outstanding puzzle of how OAM could be simultaneously described by twist-two GTMDs and twist-three GPDs. Additional relations were discussed, in particular, for the helicity configurations that can be detected analyzing specific spin asymmetries: one corresponding to a longitudinally polarized quark in an unpolarized proton, associated with spin-orbit correlations, and one for transverse proton polarization, as a generalization of the relation obeyed by the g2 structure function; finally, we defined a relation connecting the off-forward extension of the Sivers function to an off-forward Qiu-Sterman term.